1. Field of the Invention
The present invention relates in general to the field of metal working punches for the cold working of metal. The invention has particular applicability as a dual-headed punch with an improved punching head suitable for increasing the life of the tool.
2. Description of the Prior Art
A punch is used in a machining operation for the cold working of metal. A typical punch has a punching head that engages the workpiece. The head is forced, in an axial direction, through the workpiece, thereby removing the metal in its path. Punching is useful for quickly forming a rough hole in a material, and can be a preliminary to a boring operation and/or a tapping operation.
Several problems are encountered in a typical punching operation. A punch typically creates a rough hole in a metal workpiece. Due to deformation of the metal that occurs during the punch operation, the hole may not be suitably large enough. This can result in extra boring time and wear on the boring tool during the subsequent operation. Further, the punched hole may be irregular in shape, or may have metal burrs that remain along the edges. These problems lead to scrap parts, or at best, they necessitate reworking of the parts.
Tool life is a critical issue, and there is always a need for a longer life tool, especially in long-run applications such as those commonly seen in the automotive and appliance fields. Sneed U.S. Pat. No. 4,762,043, which is incorporated herein by reference, concerns a long wearing punch having first and second punching edges.
Additionally, a punch works in cooperation with a die, which has a bore to receive the punch and the metal “button” or “slug” that is removed from the metal workpiece. However, a common problem is that the slug can get caught inside the bore of the die. It can be difficult to remove the slug from inside the die, and the problem can be further complicated when multiple slugs get hung up inside the die. This can result in machine maintenance while the die is serviced or changed, resulting in loss of production due to machine down-time.